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For the use of green energy and ubiquitous computing, this study investigates miniature electric generators that are constructed with piezoelectric benders. Electric power is generated by vibratory deformation of piezoelectric benders. Three different designs of piezoelectric generators are created and compared in this study by using mechanics analysis. The result shows that the cantilever design yields more power than symmetric and airfoil designs. Experimental results show that generated voltage rises with not only attached point masses, but also the swing frequency of a swing arm, to which the proposed piezoelectric generator is attached. In addition, At 6.5 Hz swing frequency, the maximum power 0.3μW is generated.

This work employed a mixture of low-grade Mg scraps (LGMS) and citric acid-added seawater to generate hydrogen gas. Metal catalyst was not required for accelerating the reaction of H2 generation in the Mg scraps/citric acid solution. LGMS in 20 wt% citric acid-added seawater could produce substantially higher H2 volume than the LGMS in 5 wt% citric acid-added seawater. Purity of the generated H2 was about 99% (after dehumidification). By filling H2-production reactor every 30 min with fresh seawater to which citric acid has been added, ∼70 l of hydrogen could be produced in 100 min.

Direct integration of InGaN/sapphire LED with a cup-shaped copper heat spreader was proposed for enhancing light extraction and heat dissipation by self-aligned photolithography and copper electroforming techniques. Based on optical simulation results, geometric design for a copper heat spreader is crucial to luminous property of an LED chip. An InGaN/sapphire LED embedded with the optimized cup-shaped copper heat spreader was demonstrated to exhibit superior light output power than a conventional LED by a factor of 2.68 times at an injection current of 1 A. Moreover, the power efficiency is remarkably increased from 4.2% to 15.7% at the same driven current. The improved device performance can be attributed to both of the enhanced light extraction of the laterally emitted light from an LED chip and efficient heat dissipation by the highly reflective and excellently thermal conductive copper heat spreader. These results suggest an efficient alternative simultaneously with two functions of thermal management and light extraction for high-power InGaN/sapphire LEDs application from chip to package design.

As part of the trend toward an increasing fuel conscious economy, the automobile industry has increased the number of components that are produced from Mg alloy. Additionally, Mg alloy products have been widely adopted in the structure, outer shell and base seat of 3C (computer, communication, and consumer electronics) products. Therefore, from the manufacture to the end-of-life of Mg products, a very large amount of post-consumer Mg scrap is expected to be produced. This work presents a novel process for converting low-grade Mg scrap (LGMS) into H2 and Mg(OH)2. A molten LGMS bath at 580 °C in a semi-solid state was prepared. A platinum-coated Ti (Pt-Ti) net and 304 stainless steel (S.S.) net were used as metallic catalysts. A hot dipping process involved dipping the catalyst nets into the molten Mg scrap bath to obtain an Mg overlayer on the metallic net. The galvanic couple (LGMS/Pt-Ti net and LGMS/S.S. net) generated hydrogen in an NaCl solution (3.5 wt.%). The mean volume of hydrogen generated in 50 min was 28.2 ± 5.7 L as the catalyst was platinum-coated titanium and 16.1 ± 7.8 L was produced when the catalyst was stainless steel. On average, one gram of LGMS yielded approximately 1 L of H2. Experimental results concerning the metallic catalysts reveal that the platinum-coated titanium and stainless steel can be reused at least five times with comparable H2 yields. However, the performance of the catalysts gradually worsened as the number of recyclings increased.

The optical and thermal properties of blue InGaN/sapphire LEDs with a novel structure design for heat dissipation is investigated. The LED chip is designed to directly contact with a cup-shaped Cu heat spreader, and then mounted on a heat sink coated with a diamond-like film. The packaged LED chip with the novel heat dissipation design demonstrates superior light output power and reduced junction temperature as compared with the same LED chip packaged using conventional process.

In our previous studies (Chu et al. in Heat Mass Transf 43(11):1213–1224, 2007), a theoretical model of swirl atomizers was successfully established. From the analysis, the equations for the droplet size, velocity components, the boundary layer thickness and the spray cone angle were deduced based on the fundamental governing equations. The purpose of this study is to further compare the experimental result with the theoretical one already gained by a satisfactory embodiment of series of experiments. The aim is to corroborate the analytical results of the influence of atomizer construction and controlled pressure difference on typical swirl chambers. The results provide the droplet diameter as a function of pressure difference, swirl atomizer geometry, flow rate, spray cone angle. The experimental outputs also show a good confirmation of theoretical results and can also be used for further optimization on existing swirl chambers. Based on the results obtained, an optimization methodology on characteristics of swirl atomizers is proposed with the adjustment of individual design parameter and the matching flow number.

In this study, theoretical analyses have been performed to investigate the effects of atomizer construction and controlled pressure difference of swirl atomizers. The analysis of fluid field in the swirl chamber is governed by mass/energy conservation rules; in the region outside the nozzle, the analysis of oscillation of liquid sheet is based on Squire’s expression for the amplitude growth rate. With some physical assumptions of control volume, initial values and model correlation, analytical results make it possible to predict film thickness, velocity distribution, spray cone angle and droplet size directly. The distribution of velocity profile and boundary layer thickness in the swirl chamber have been established with the aid of MATLAB. Based on the results we obtained, we here propose the change of individual design parameter and its corresponding flow number to optimize the performance of swirl atomizers.

Silicon nitride (SiNx) films deposited on Ar, N2, and O2 plasma-treated polycarbonate (PC) substrates have been investigated for transparent barrier applications. The details on different gas effects on PC surface and SiNx/PC properties were investigated in terms of the contact angle, free energy, roughness, adhesion, transmittance, water vapor transmission rate (WVTR) and oxygen transmission rate (OTR). It was found that both Ar and N2 plasma could improve the adhesion between SiNx films and PC substrates. When the roughness of plasma-treated PC substrates was decreased from 1.71 nm to 0.89 nm, the OTR data of SiNx/PC samples after 6000 times bending test was decreased from 0.61 to 0.1 cm3/m2/day. Moreover, the transmittance and permeation results of SiNx/PC plasma-treated samples also show great dependence. After Ar plasma treatment for 60 s, the WVTR and OTR of the 50-nm-thick SiNx barrier coating on PC substrate after 6000 times bending test can decrease to a value of near 0.01 g/m2/day and 0.1 cm3/m2/day, respectively. This result indicates that the SiNx films on Ar plasma-treated PC substrates have high potential for flexible organic light-emitting diode applications.

Silicon nitride (SiN X ) deposited on flexible polycarbonate (PC) substrates by plasma-enhanced chemical vapor deposition have been investigated for thin-film barrier applications via the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) measurements. A cyclic bending test was used to get quantitative information about the OTR and WVTR data of the single thin brittle SiN x /PC film with various thicknesses (50–400 nm). It was found that the SiN x /PC sample with a thickness of 100 nm possessed a minimum saturated crack density, as evidenced by the lowest OTR/WVTR values after the cyclic bending test. To improve the barrier performance, a smoothing, defect-decoupling organic film (parylene) was deposited on the top of the SiN x layer. The degradation after the cyclic bending test for the parylene/SiN x /PC structure was improved more than one order of magnitude as compared with that for the SiN x /PC sample. After 3000-times cyclic bending, the WVTR and OTR of the two pairs of parylene/SiN x coatings on PC can be maintained at a level near 0.01 g/m 2 /day and 0.1 cc/m 2 /day, respectively (below the detection limits of the MOCON systems). These indicate that the present multilayered coatings have high potential for future flexible display applications.

Silicon nitride (SiN x ) films deposited on flexible polyethersulfone (PES) substrates by plasma-enhanced chemical vapor deposition (PECVD) have been investigated for water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) barrier applications. Details of the NH 3 /SiH 4 flow ratio and chamber pressure effects on the SiN x /PES properties in terms of chemical bonding, transmittance, refractive index, deposition rate, adhesion, roughness, OTR and WVTR were investigated. When the NH 3 /SiH 4 flow ratio increased from 1.43 to 10, evident variations in refractive index and transmittance of the SiN x /PES samples were observed. Moreover, as the chamber pressure increases from 26.7 to 133.4 Pa, the deposition rate, adhesion and roughness increase while no evident variations in WVTR and OTR were observed. Under optimum conditions, the WVTR and OTR of 100-nm-thick SiN x barrier coating on PES at 150 °C decreased to a value of near 0.01 g/m 2 /day and 0.01 cm 3 /m 2 /day, respectively. This indicates that the SiN x barrier on PES has high potential for flexible display applications.

Silicon oxide (SiOx) films deposited on flexible polyethersulfone (PES) substrates by plasma-enhanced chemical vapor deposition (PEVCD) have been investigated for transparent barrier applications. Although the water vapor transmission rate (WVTR) of PES (∼28 g/m2/day; thickness: 200 μm) is higher than that of the polyethylene terephthalate (PET; ∼16 g/m2/day; thickness: 188 μm), the PES substrate can withstand process temperatures of up to 180 °C, providing more flexibility in the design of device processing. Details of the substrate-temperature and film-thickness effects on the SiOx/PES properties in terms of transmittance, refractive index, deposition rate, adhesion, roughness, and WVTR were described. When the substrate temperature increased from 80 to 170 °C, the deposition rate, adhesion, and roughness values were found to increase while the WVTR decreased to a value of near 0.3 g/m2/day at 150 °C. With increasing the oxide thickness from 50 to 500 nm, the surface roughness increased from 2.71 to 5.84 nm. A lower WVTR value can be achieved under a barrier thickness of 200 nm. Further improvement was carried out by depositing a 100-nm-thick SiOx film on both sides of the PES substrate, which resulted in a minimum WVTR of 0.1 g/m2/day. The double-sided coatings on PES could balance the stress and greatly improve the WVTR data.

A vertical twin-parallel-tube absorber-evaporator unit was built for the present study to investigate the overall heat transfer and mass absorption rates at various operation conditions. In order to establish the optimal surface wetting condition for the thin absorbent film during operation process, an annular-slot type solution distributor with declining surface was adopted for the present system. The main objective of the present study is to perform an experimental investigation of the controlling parameters associated with absorption by falling film, including the operation pressure, the inlet temperature of the cooling water, and the Reynolds number, temperature, and concentration of the inlet absorbent solution. An analogy between heat and mass transfer near the film surface is then applied to calculate the interfacial concentration and temperature of the absorbent film, and thus the heat and mass transfer coefficients of the absorbent film is determined. The present results show that, the higher the inlet Reynolds number of the absorbent solution is, the lower the total heat transfer rate is. Increasing operation pressure will increase the concentration difference of the absorbent solution. The concentration difference of absorbent solution film between inlet and outlet increases sharply as the Reynolds number of the inlet absorbent film decreases below 200. When the Reynolds number of the inlet absorbent film is around 200, optimal absorption-evaporation exists and will provide appropriate conditions for a high efficiency absorption air conditioning system.

A new vacuum freezing ice production (VFIP) method based on the solid‐liquid‐vapor multiple phase transformation and the latent‐heat coupling mechanism is introduced in the present study. Coupled heat and mass flux equations based on irreversible thermodynamics have been applied to depict the ice growing phenomenon under vacuum, and to derive an equation for its growth rate. Ice growth rates of the VFIP model determined are much higher than the ones in the conventional freezing model which is for ice production at atmospheric pressure. The concept of equivalent ice‐layer thickness δeq with respect to the specific water film thickness δl , and a design guideline for optimal operation are also introduced in the present study. With the unique feature of a spontaneous temperature gradient developed inside the ice layer of VFIP, an extremely fast and energy‐saving ice‐block production method is found to overcome the disadvantages in energy consumption and ice growth rate of conventional methods.

To improve light extraction efficiency and heat dissipation of sapphire-based light-emitting diodes (LEDs), we develop and optimize copper heat spreader which was electroformed in close contact with sapphire. On the basis of simulation results, an LED with copper lowers junction temperature when compared with the LED without copper. In addition, a copper-surrounded LED with protruded bottom surface exhibits almost the same thermal performance as that with flat bottom surface. In practical fabrication, all the LED samples with copper show significant reduction in junction temperature form 150.4°C for the original LED to less than 100°C at injection current of 1 A (∼ 3 W/mm2). The encapsulated LED at the same driven current yields an output power of ∼700 mW, which is 2.7 times higher than that of the original LED without copper.

To transform endless energy from ambient vibration into useful power. We scavenge mechanical energy and transfer into electrical energy by utilizing piezoelectric materials. We compare generators performance at different situations and then let electric energy be charged to a Ni-MH battery or a capacitor through a full wave rectifier. We also obtain resonance of piezoelectric benders by system identification which can be an important reference when designing the generator. This study proposes a novel mechanism comprising a mass-spring system and magnet repulsive force. According to finite element software and experimental result, below 5 Hz the generator absorbs vibration energy more easily. We have investigated the influence of the mass magnitude and obtained the optimum result of 2.7 V and 0.379 muw when the swinging amplitude of the motor is plusmn1.8 deg at swinging frequency of 3.96 Hz.

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